1. Field of the Invention
The present invention relates to a communication initialization method at a Medium Access Control (MAC) layer in a Cognitive Radio (CR) wireless communication system.
2. Description of the Related Art
Along with the rapid development of wireless communication systems and a variety of wireless communication services, strict frequency separation is required for coexistence with legacy communication systems. There is also a short supply of spectrum frequencies due to multiple allocations over all of the frequencies which can be commercially used. Deployment of a new wireless platform faces a serious shortage of spectrum resources, particularly in lower frequency bands than a few gigahertzes. To solve this spectrum shortage, the concept of CR has been introduced, which is a frequency-agile technique for sensing allocated but unused spectrum and efficiently sharing the detected spectrum.
Many countries have strictly regulated the use of frequency resources subject to their frequency policies, and service providers use frequencies through licensing and allocation from their governments. As opposed to legacy wireless communication systems, the CR technology enables the use of allocated but unused frequency resources in a non-interfering manner with wireless communications from legacy service providers.
In order to meet the recent increasing demand for limited frequency resources, there is a pressing need for the CR technology, which has attracted much interest since the U.S. Federal Communications Commission (FCC) commented on the possibility of frequency sharing in a Notice of Proposed Rule Making (NPRM) in December 2003. Such a major example is the standardization of the Institute of Electrical and Electronics Engineers (IEEE) 802.22 Wireless Regional Area Network (WRAN) seeking the development of a CR communication platform. The IEEE 802.22 WRAN system is expected to be deployed in suburban areas of the U.S. or Canada, or in developing countries, aiming to provide wireless communication services using the CR technology in an unused TV frequency band.
CR standardization and development is active but in an early stage. There still exists many issues to be handled and most of configurations for the CR technology are yet to be specified.